/*全局*/
div:not(.background){
    margin: auto;
    background-color:  #64b5f6;
    
    border-radius: 20px; 
}

h1{
    color: #e0e0e0;
    font: size 20px;
    text-align: center;
}

p{
    text-align: center;
}


/*类*/
.div1{
    width: 700px;
    height: 100px;
    
}



/*id*/
#div2{
    width: 200px;
    height: 100px;
    /*关键帧名字*/
    animation-name: div2;
    /* 关键帧运行秒数 */
    animation-duration: 2s;
    /* 关键帧运行模式 */
    animation-direction: alternate;
    /* 关键帧运行次数 */
    animation-iteration-count: infinite;
}

#wuhu{
    color: aqua;
}

#biankuan{
    border:solid #e0e0e0;
    border-width: 10px;
    border-radius: 10px;
}

/*动画*/
@keyframes div2 {
    0%{width: 0px};
    25%{width: 50px};
    50%{width: 0px};
    75%{width: 10px};
    100%{width: 50px};
}
